I found that the Purolator A25306 will better fit the A1,2,3,4 and 5 Mule Canister with 1 modification. I punched a 1-7/8 inch hole in the bottom of the filter and it sits flat and secure on the bottom of the canister and the rubber wraps up on the protrusion creating a tight seal. Very difficult to get a good hole using scissors or a razor knife.